Method of injection molding a tote case



1956 R. 1.. BEESLEY ETAL 3,264,396

METHOD OF INJECTION MOLDING A TOTE CASE 2 Sheets-Sheet 1 Filed Jan. 6,1964 m mfi T r mafi ve JM mB um Wyn m 3k.

United States Patent METHOD OF INJECTIbN MOLDING A TOTE (ZASE Robert L.Beesley, Saginaw, John W. Mighton, Midland,

and Rudolph H. Matthias, Saginaw, Mich, assiguors to The Dow ChemicalCompany, Midland, Mich, a

corporation of Delaware Filed Jan. 6, 1964, Ser. No. 335,739

4 Claims. (Cl. 264328) This invention relates generally to tote casesand, more particularly, relates to tote cases particularly suited forhandling products such as paperboard and plastic liquid containingpackages, and to the method of making such cases.

Prior plastic tote cases fail to provide satisfactory stacking of aplurality of such cases as well as fail to provide a case bottomstructure having adequate drainage facilities and yet being ofsufiicient strength to endure harsh treatment.

Yet another object of the present invention is to provide a bottomstructure for a tote case which is of such a configuration that when itis formed, uniform controlled material distribution in parts can be hadeven though it be of a generally square or other rectangularconfiguration.

Briefly then, the present invention thus resides in an improved plastictote case having all the advantages of the prior cases plus improvedstacking characteristics due to an offset shoulder and outwardlyextending protuberances. Recessed internal corners are provided in thecase which substantially prevent corner fitting of rectangularly shapedcartons. Also comprehended is an improved bottom construction whichprovides adequate drainage while retaining substantial strength.Co-extensive with the above is a method for forming the bottomconstruction which method provides for a uniform control of materialdistribution in the molding thereof.

Yet additional objects and advantages of the present invention, and itsnumerous cognate benefits and features are even more apparent andmanifest in and by the ensuing description and specification taken inconjunction with the accompanying drawing in which, wheresoeverpossible, like characters of reference designate corresponding materialand parts throughout the several views thereof, in which:

FIGURE 1 is a side view of a tote case constructed according to theprinciples of the subject invention, all sides being substantiallyalike;

FIGURE 2 is a top plan view thereof;

FIGURE 3 is a bottom view thereof;

FIGURE 4 is an enlarged fragmentary section of two tote cases stackedtogether, the bottom of an upper tote case stacked upon the top of alower tote case; and

FIGURE 5 is a bottom plan view of a modified form of tote case having anelongated rather than a square bottom configuration.

Tote case or container is illustrated in FIGURES 1-4 as having asubstantially square bottom 11 with side walls 12 extending upwardlytherefrom. It is best molded from a lightweight plastic material such ashigh impact polystyrene or rigid polyethylene, or of other plasticmaterials having like characteristics. The four side walls 12 ofcontainer 10 preferably have a corrugated crosssection formed byundulations 14 to provide increased stacking rigidity, improved controlof warpage, minimal moisture condensation, and faster cool-down of thecontainer and contents. Such undulations 14 have been found especiallyuseful in thin walled plastic cases. Corners 15, formed by adjacent sidewalls 12, are recessed so as to prevent a tight mated fit with cornersof cartons, or the like, contained within tote case 10.

3,264,396 Patented August 2, 1966 "ice It is noted that each side wall12 has hand opening 16 with a lip or raised flange 18 around theperiphery thereof to provide a reinforced grip. Formed around the upperperiphery of each side wall is a thickened portion 20 which concludes indownwardly extending corner portions 22, the latter containing holes 24which can be engaged by hooks or the like when the cases are pulledmanually or are moved by heavy equipment.

The lower end of each side wall 12 merges into bottom 28 by way of arecessed shoulder portion 26 which gives a generally flat verticalsurface 30 with bumps or rounded tapered protuberances 32 located inspaced relationship therealong, as best seen in FIGS. 1 and 4.Protuberances 32 act as spacers juxtapositionable with the inner surface34 about the top of a stacked tote case of a similar configuration.Preferably, protuberances 32 extend from the surface 30 a distance so asto snugly engage inner surface 34 to give added rigidity to the stackedcases. It can readily be seen that shoulder 26 rests upon the upperperipheral edge 36 of the case therebelow.

FIGURE 3 especially shows that the bottom 18 of tote case 10 is formedabout a plurality of cut-outs 38 which provide the improved drainagecapabilities of the case, both when it holds containers and when it isin a plant, such as a dairy, being cleaned. The cut-outs 38 are definedby crossed planar portion 40 which is in turn reinforced by downwardlyextending ridges 42 along approximately all of its surftce. The T-shapedcross section construction formed by planar portion 40 and downwardlyextending rib 42 give improved rigidity. Cut-outs 38 are generally inthe form of parallelograms except about the periphery of the bottomwhere they are in the form of triangles approximately one-half the sizeof the parallelograms. The crosses formed by planar portion 4t) compriseat least linear diagonals extending generally across said bottom wallbetween opposite corners thereof.

In forming such a container and its bottom configuration, plasticmaterial is injected into a mold in equal directions from the center ofthe bottom through a gate (not shown). The location of the gate isdefined in FIG- URE 3 by central aperture 44 which is surrounded bythickened peripheral flange 46. When a case is injection molded, plasticflows from the center portion, under pressure, in a flow patternsubstantially as defined by surfaces 40' and ribs 42, which patternmakes the distance from the orifice of the gate to peripheral pointsaround the sides, such as 48, 50, 52, etc., the same. Thus, the distancethrough which the material must flow, i.e. from the gate to the cornersor the side walls, is the same in every instance. Such uniformcontrolled material distribution in molded cases having square orrectangular bases eliminates the prior problems caused by warping, poorweld lines, packing stress, and all the other inherent characteristicsin prior art designs.

That an elongated rectangular base for a'tote case can likewise haveuniform material distribution when molded through a central gate isillustrated by FIGURE 5. For example, here the flow distance fromcentral aperture 54 of case 56 to the corners, such as corner 58, is thesame as the flow distance to any point on the sides, such as to points6%) or 62, the distance being defined by ribs 64. Ribs 64 in thisinstance define cut-outs 66 in the shape of parallelograms about thecenter and triangles about the periphery of the bottom.

While certain representaive embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in the art that various changes and modifications can be madetherein without departing from the spirit and scope of the invention.

Accordingly, What is claimed as new is:

1.- The method of forming a molded plastic tote case 7 having arectangular bottom, said method comprising the step of injectingthermoplastic material from the center of said bottom along a pluralityof flow lines which cross one another and are of the same length to theperiphery of said bottom, whereby uniform controlled materialdistribution is maintainedv 2; The method of claim 1 wherein said flowlines are step of injecting thermoplastic material from at leasta pointin a plurality of intersecting flow lines which is substantiallyequidistant from the furthermost extents said material must travelthrough said flow lines, said flow lines arranged to define a pluralityof like parallelograms in rows.

having a rectangular bottom, said method comprising the References:Cited by. the Examiner.

UNITED STATES PATENTS 3/1940 Tegarty 1830 9/1947 Stacey 1842 1 12/1956Knieriem 220-97 8/1958 Pollard 264-328 10/1961 Lovell; -2 23097 10/1961Gustafson 220 10/1963' de Chelbor 220-21 4/ 1964 W0rmer 220-21 5/1964Peters 264--328 12/1964 Herter 264-328 1/1965 Box- ,22021 FOREIGNPATENTS 8/1960 France.

3/1962 France.

1/ 1957 7 Germany.

ROBERT F. WHITE, 'Primary Examiner.

GEORGE E. LOWRANCE, Examiner.

R; B. MOFFITT; Assistant Examiner.

1. THE METHOD OF FORMING A MOLDED PLASTIC TOTE CASE HAVING A RECTANGULARBOTTOM, SAID METHOD COMPRISING THE STEP OF INJECTING THERMOPLASTICMATERIAL FROM THE CENTER OF SAID BOTTOM ALONG A PLURALITY OF FLOW LINESWHICH CROSS ONE ANOTHER AND ARE OF THE SAME LENGTH TO THE PE-